The present invention relates generally to CLV (Constant Linear Velocity)-type recordable optical disks having track wobbles and apparatus for recording desired information onto such optical disks, and more particularly to a technique of minimizing unwanted cross-talk between wobble signals from adjoining tracks.
In recordable optical disks based on CD standards, such as CD-R (CD-Recordable) and CD-RW (CD-Rewritable) media, a plurality of tracks are previously formed as guide grooves, each of which wobbles typically at a fixed frequency of 22.05 kHz and has recorded thereon address (ATIP: Absolute Time In-Pregroove) information, indicative of absolute positions in the track, in FM-modulated form. The track wobbles are used as detection signals for disk rotation control at the time of recording on the optical disk, and are also used to generate reference clock pulses for the recording. Further, wobble signals detected from the optical disk during the recording are FM-demodulated to acquire the address information.
Further, in DVD-R (Digital Versatile Disk-Recordable) media, tracks are previously formed as grooves each wobbling typically at a fixed frequency of 140 kHz without modulation. Address information is recorded as pre-pits in lands (between the grooves). In this case too, the track wobbles are used as detection signals for disk rotation control at the time of recording on the disk.
In recording desired information onto such optical disks with the track wobbles, however, wobble signals from adjoining tracks tend to be detected as cross-talk signals. Particularly, with high-density optical disks, the cross-talk would occur in a considerably great amount because the track pitch is reduced relative to the size of a light spot irradiated onto the disk. With the CLV (Constant Linear Velocity)-type disks, the wobble signals, detected by the push-pull scheme, would be greatly modulated in both amplitude and phase by the cross-talk signals, resulting in beat signals. Thus, in the case where the address information is recorded in the track wobbles, the phase modulation by the cross-talk causes the address information to jitter, which would prevent accurate data-write linking. These jitters also lead to jitters in the recording reference clock pulses generated from the wobble signals, which would also prevent accurate data-write linking and degrade the quality of recording signals.